Combined adjustable resistance device and switch unit



H; F. NIED 1 1 COMBINED ADJUSTABLE RESISTANCE DEVICE AND SWITCH UNIT 7 Filed March 11, 1940 2 Sheets-Sheet 1 Feb. 16, 1943.

Snventor HermmENwzb, y s

2 I attorneg Feb. 16, 1943. H. F. NlED 2,311,611

COMBINED ADJUSTABLE RESISTANCE DEVICE AND SWITCH UNIT Filed March 11, 1940 2 Sheets-Sheet 2 3 nne nfor flermnlt jvwdg u attorney Patented Feb. 16, 1943 UNITED STATES PATENT OFFICE COMBINED ADJUSTABLE RESISTANCE DEVICE AND SWITCH UNIT Herman F. Nied, Camden, N. J.

Application March 11, 1940, Serial No. 323,488

1 Claim. (01. 201-55) My invention relates to an adjustable resistance device and relates more particularly to a device adapted to be used advantageously in an electrical circuit of a radio receiver or of a public address system for the purpose of controlling the intensity of sound or the tone of sound.

Adjustable resistance units heretofore have been employed alone or in conjunction with switches to control the source of the electrical energy. In the small type of adjustable resistance device or rheostat, it has been customary to have the rotatable control shaft oscillate less than 360 because the useful arcuate length of the resistance element when measured in an arcuate direction is less than 360. In certain cases, it is desirable to vary the position of the stop member in order to vary the effective length of the resistance element. In volume controls heretofore known, the effective length of the resistance element could not be adjusted after the resistance element had been assembled into the volume control or rheostat, and one of the principal objects of my invention is to provide an adjustment on a volume control for varying the effective length of the resistance element.

Another object of my invention is to provide a pressure member cooperable with the resistance element contact arm wherein the pressure member also serves to limit the rotation of the control shaft.

Another object of my invention is to provide a volume control having a two-bearing support for the rotatable control shaft.

Another'object of my invention is to provide in a volume control a stamped metal housing having a stop member formed integrally therewith, which stop member may be easily displaced to vary the usable length of the resistance element.

Another object of my invention is to provide a combined adjustable resistance device and electrical switch unit, both of which are actuated by a single rotatable control shaft and wherein the electrical switch actuator is mounted directly upon the control shaft.

Other objects of my invention are to construct an improved device of the character described which is readily and economically produced, that is sturdy in construction, and which has a maximum degree of eificiency in operation.

. With the above and related objects in view, my invention consists in the details of construction and combination of parts, as will be more fully understood from the following description when read in conjunction with the accompanying drawings, in which:

Fig. 1 is a side View of a combined electrical adjustable resistance device and electric'switch unit embodying my invention.

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1.

Fig. 3 is a sectional view taken on the line 33 of Fig. 1.

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 6.

Fig. 5 is an enlarged fragmentary perspective view of the adjustable control arm stop members.

Fig. 6 is a fragmentary view through the side of the volume control embodying my invention.

Fig. 7 is an exploded view of most of the elements comprising my invention with one casing and holding bushing omitted.

Fig. 8 is a perspectiveview of one of the casing members. r

Referring now in detail to the-drawings, I show in Fig. 1 a combined volume control or adjustable resistance device combined with an electric switch wherein my invention is embodied.

The rheostat or adjustable resistance device has a stamped metal housing or casing of cylindrical form, generally designated as A, which casing comprises a base Ill, a flange [2, extending at right angles to the base l0, and a pair of diametrically opposed, longitudinally extending positioning arms 36, each terminating in a pair of lugs 58 and 60 (see Fig. 8). The casing A may serve as an electromagnetic and electrostatic shield when grounded.

A central aperture in the base I0 has a shaft bushing, generally designated as B, passing therethrough. The bushing B holds the entire volume control unit and switch on a mounting panel (not shown) by means of a lock nut (not shown). This is the well-known single hole volume control mounting.

Journaled within the bushing B is a rotatable shaft, generally designated as C. A split 6- Washer l4, set in a complementary groove in the shaft C, is adapted to abut one end of the bushing and limits the movement of the shaft C in one longitudinal direction.

Intermediate the ends of the shaft C and within the casing A is an insulating control head, generally designated as D, which supports a contact arm, generally designated as E. The ends of the contact arm are adapted to, slide in engagement with a resistance element, which is generally designated as F. The resistance element is of general arcuate formation and will hereinafter be further described.

The resistance element F is mounted upon an insulating disc, which is generally designated as G, and which is adapted to overlie the open end of the flange l2. Stationary terminals l6 and I8 are respectively connected electrically to each end of the resistance element F by means of suitable rivets or grommets 20 of electrical conducting materials.

The contact arm E is mounted on that surface of the control head D which is closest to the resistance elements F, and on the opposite side of the volume control head is a spiral spring, generally designated as Q, which has one end connected to a rivet 20 so that an electrical contact is formed between the contact arm E and the spiral spring. The other end of the spring Q extends through an opening 2| in the base Ill so that contact may be made between the contact arm. E' and a terminal 22. Thus, there will be different potential drops between either one of the arms H or 18 and the terminal 22 depending on the position of the contactarm E onthe resistance element; however, the-potential'drop between the terminals 16 and I8 will'be constant.

An insulating thirnble or spacer 2'4 prevents any electrical contact between the control shaft C and the spiral spring Q. The spiral spring Q serves to complete the electrical circuit from the contact arm E to the outside terminal 22, and it eliminates any sliding contact between the contact arm E and'the outside terminal 22, which sliding contact, if present, is normally subject to corrosion.

A- ring-like insulator 26, mounted within the metal casing A, lies adjacent theinside wall' of the base l0 and serves to support a holding rivet which carries theterminal 22, the latter-overlying a part of the opening 2| in the base In. The'i'nsufat'or 26 also serves to close'the'opening 2| in the wall H] of housing A so that dust and dirt will be excluded from entering the housing through that particular opening.

The terminals l6 and IB' electrically connected to the respective ends of the resistance element F lie adjacent the face of the base G'opposite tothat onwhich the resistance element F lies, the insulatingbaseG having a central shaft opening 28 therein. A second insulating washer, generally designated as H, is adapted to overlie the resistanceelement base G, and it has a central shaft opening 30 aligned with the central opening 28. The washer H has recesses 3| and 32 in its periphery for the purpose of complementing the terminals l6 and I8, respectively. The thickness of the insulator H is equal to or slightly greater than the thickness of the electrical terminals It and I8, and the insulator H also may have additional complementary recesses for additional terminals, if it should be found desirable to add additional terminals.

overlying the insulator His another insulator. enerally designated as G, which is of the same general structurean'd made of the same insulatin material'- as the insulator" G. The insulator G" has a central opening 39, which serves as a second bearing for the control shaft in the disc-like base 38, and a flange extending at right angles to the edge of the base is integrally formed with the base 38. The flange of the casing J does not have a constant radius from the center of the base as the flange diameter increases adjacent each of the openings 34, as at 42. The flange portions 42 of the switch housing are on a greater diameter than the flange portions 40, and this increase in diameter is for the purpose of receiving the positioning arms 35. The shaft C is sufficiently long to extend from the front of the bushing B clear I through the bushing B, the casing A, and into the casing J The base 53 also has an upturned wing 44, which is substantially T-shaped and serves as a stop member for the control shaft, the Wing 44 being adapted to be bent or twisted through approximately 90 for a purpose to be presently set forth. Mounted upon the end of the shaft C and within the interiorof the casing J is a combined arm' and spring washer, generally designated as K, having two convex contact members 4| and 43 forengagement with the base 38 to hold the parts heretofore. described firmly together. Adjacent the spring arm K is a combined holding member and switch actuator, generally designated as L. Thecontrol shaft at its outer: end has two substantially flat sides, and the combined: spring washer and contact arm K has a complementary opening, which drivingly' receives the control shaft 0, so that rotation of the control shaft: also rotates. the arm K within certain limits, as shall hereinafter be further defined;

The snap switch. actuat'orzL. likewise has a complementary opening'for. the substantiallyrectangul'ar portion. of the control. shaft C so that rotation of the control shaft also rotates or oscil-' lates the. switch actuator L. The end of. theshaftl C'is peened over so that the spring? arm K and the switch actuator L are firmlylo'cked to' the shaft C, and rotation of' the shaft C moves or oscillates in unison therewith the contact arm E, thespring arm K", and the switch actuator L.

As pointed out above, theresistance element F' is mounted upon one side of the insulator G, and the terminals It and I 8' are mounted uponithe opposite side; and the resistance elementF is in one casing, and the switch actuator L is in. a

second casing, although the variation of the resistance and the control of the'switch are efile'cted by one shaft.

The control shaft C is flattened on its'p'eriphcry to cooperate with complementary'flat' surfaces on the control head D, the spring arm K; as well as the switch actuatorarm L, so that the aforesaid elements move in unison with the control' shaft.

When the casing J is grounded, it serves as an electrostatic and electromagneticshield between the volume control or rheostat F and a switch, about to be described in greater detail.

The electric snap switch, generally designated as S, is mounted within a Bakelite casing or'a' casing preferably molded of a phenolic condensation product under suitable heat' and pressure and formed with peripheral slots or seats on its outside curved peripheral surface for accomimodating the positioning arms 36. The. details of construction of the switch do not forma part of this invention and, therefore, are only generally referred to. The switch has a trigger, gen-- erally designated as M, which comprises two spaced members 45 and 48. Each member 46- and 46 is adapted to be contacted by the actuator arm L depending, of course, on the position of the arm; that is, the trigger M of the switch S will only be actuated when it is in the path of travel of the actuator L.

A torsional spring, generally designated as N, is positioned between a throw arm, generally designated as P, and the trigger M. The throw arm P carries the customary short circuiting or bridging member 53, which is adapted to shortcircuit electrical power terminals 52 and 56. Movement of the trigger M does not actuate the throw arm P until the medial axis of the closed end of the spring passes slightly beyond dead center as the trigger compresses the torsional spring N. The ener gy stored in the spring after the dead center position of the spring is passed rapidly turns the throw arm P and its short circuiting member 56, the latter either closing the electrical circuit when the terminals 52 and 56 are bridged by it, or breaking the circuit when it is moved away from the terminals.

In assembling the parts, the positioning arms 36 are inserted through the openings 34 of the casing, after which the switch casing is mounted on the arms 35, the latter fitting into the slots 45 of the switch casing and the switch casing being pushed down along the arms 36 until it abuts the edges of the flange portions 40 of the casing J. The flange portions 42 on the casing J firmly fit about the arms 36 so that the casing J cannot move transversely or rotate with respect to the central axis, either by accident or by intent. The casings A, J and S are firmly held together when the ears or lugs 58 and 60 are bent over the casing S.

Each of the insulating discs G, H and G have suitable notches 62, 64, and 66, respectively, on their periphery to partially engage the edges 55 and 51 of the arms 36 so that the insulating discs will not rotate or fall out of position; that is to say, the edge 55A of notches 62 on disc G cooperates with the edge 55 on one arm 36; and the edge 57A of notch 62 of the disc G is adapted to engage the edge 51 on the same arm 36. Similar cooperation takes place between the disc G and the other arms 36, as well as the arms 36 and the other discs G and H. The arcuate distance between the edges 55A and 51A is substantiailly equal to the arcuate distance between the edge 55 and the edge 51.

The resistance element F may have suitable hop-off resistances, and. it also may have suitable taps for automatic volume control or for tone control terminals. If it should be found, after assembly of the casings A and J, that the contact arm E should come to rest at a point closer to or farther from the end terminal of the resistance element F, a suitable adjustment may be made by twisting the stop 44 as much as with a pair of pliers. Thus, when the stop 44 is twisted or bent to the position shown in Fig. 5, the spring cam K and the contact or slider arm E have a greater range of movement relative to the resistance element F than if the stop 44 is in the position shown in Fig. 3.

For example, in Fig. 3 the terminal 44 is stamped out of the base 38, an extension 41 on the arm K engages one end of the cross arm of the T-shaped stop 44; whereas in Fig. 5, the stop 44 has been turned 90 with a pair of pliers so that the arm K is adapted to engage one face of the cross arm of the T, thereby permitting a greater arcuate movement of the contact arm E over the resistance element F. The distance or arcuate length of the resistance element over which the contact arm E can move may thus be varied after the volume control has been assembled without the disassembly of the unit. This is believed to be an important advance over the prior art devices.

The switch S is actuated by the control shaft C being rotated so that the actuator L engages one fork of the snap switch trigger, and movement of the control shaft in the reverse direction closes the switch. Actuation of the switch, however, only occurs during a small arcuate movement of the control shaft, and further movement changes the effective resistance between terminals and 22 and terminals l6 and 22.

Although my invention has been described in considerable detail, such description is intended as illustrative rather than limiting, since the invention may be variously embodied, and the scope of the invention is to be determined as claimed.

I claim as my invention:

In a volume control, the combination of a resistance element, a contact member slidably associated with said resistance element, a second member connected with and movable in unison with said contact member and a stop member of bendable material associated with said second member for limiting the movement of said contact member relative to said resistance element, said stop member being substantially T-shaped and the leg of said T being adapted to be twisted through at least 90 degrees whereby, in one position of said stop member, said second member is adapted to engage one end of the cross arm of said T, and when said leg is twisted through 90 degrees said second member is adapted to engage one side of the cross arm of said T.

HERMAN F. NIED. 

